What if you could power your phone on a single AA battery? The SpareOne is a mobile phone that can to do just that. Designed as a back-up that you keep in a glovebox or emergency kit rather than a phone you keep in your pocket everyday, the SpareOne claims to deliver you up to 10 hours of talk time on one AA battery and (depending on the shelf-life of the battery you're using) it can hold charge while unused for up to a whopping 15 years.